Updraft biomass dense baking and conditioning method

Abstract

The application discloses a biomass updraft dense baking and humidifying method, which is an improvement on traditional baking technology, and is designed according to tobacco baking characteristics and tobacco loading density and comprises the following steps: baking preparation - setting parameters, ignition baking - window opening baking, automatic air feeding - temperature stabilizing and humidity adjusting, bottom layer yellow softening - air speed adjusting, middle layer yellow softening - up-down humidity adjusting, manual air feeding, top layer yellow softening - humidity stabilizing, stable branch vein white, continuous air feeding, leaf hooking - humidity stabilizing, stable large vein white, continuous air feeding, half-dry leaf - humidity stabilizing, stable large exhaust, continuous air feeding, full-dry leaf - reducing ventilation and exhaust, main vein contraction and purple - air door gap, and main vein full dryness. The method has strong operability, can reduce problems such as mold, flowered leaf, ash sticking, black dregs and green baking in the tobacco baking process, improves the appearance quality of tobacco, makes the chemical composition of tobacco more coordinated, and improves the tobacco yield and usability.

Description

Technical Field

[0001] This invention relates to a biomass rising intensive curing and humidity control method, belonging to the field of tobacco curing technology. Background Technology

[0002] Tobacco curing is the most crucial step in flue-cured tobacco production, determining the quality, yield, and usability of cigarettes. It is also a major factor directly impacting tobacco farmers' income and the quality and economic benefits of the cigarette industry. The quality, use value, and economic value of tobacco leaves are jointly determined by field growth management and scientific curing. Therefore, curing is of paramount importance in tobacco quality and flue-cured tobacco production. The curing characteristics, processes, and quality of flue-cured tobacco leaves are closely related and form the basis for developing suitable curing methods and creating optimal curing conditions to produce the best quality tobacco leaves.

[0003] Currently, in the intensive roasting process of biomass, some areas still adopt the traditional roasting technology of low temperature and humidity for slow yellowing, rapid temperature rise, large ventilation, and low humidity for color fixing and drying of the gluten. The specific process is as follows:

[0004] The first step is to load the tobacco onto the kiln, close the doors and windows, set the baking process parameters, adjust the baking curve status indicator box to the initial position, adjust the circulating fan to low speed, and start baking.

[0005] The second step is to maintain the starting dry and wet bulb temperature of 32℃ and bake for 12-18 hours. After the tips of the bottom tobacco leaves turn yellow, increase the temperature by 1℃ / h to 36℃ for both dry and wet bulbs and bake at a stable temperature for 12-18 hours. The program automatically controls the opening of the cold air inlet door and the dehumidification window blades, and the circulating fan is kept at a low speed. Bake until the bottom tobacco leaves are 80% yellow and the leaves expand.

[0006] The third step is to raise the temperature at 1℃ / h to 38℃ for dry bulb and 36.5-37℃ for wet bulb, and bake at a stable temperature for 12-18 hours. The program automatically controls the opening of the cold air inlet door and the dehumidification window blades, and the circulating fan keeps the speed low until the bottom tobacco leaves are yellow with green veins and the leaves are slightly soft.

[0007] The fourth step is to adjust the circulating fan to medium speed and raise the temperature at 1℃ / h to 40℃ for dry bulb and 37-39℃ for wet bulb. Maintain the temperature for 6-12 hours and automatically control the opening of the cold air inlet and exhaust window blades. Bake until the middle layer of leaves turns yellow with green veins and the blades are slightly soft, and the bottom layer reaches the point where the veins turn white and half of the blades are soft.

[0008] Step 5: Increase the temperature at 1℃ / h to 42℃ for dry bulb and 38-40℃ for wet bulb, and bake at a stable temperature for 12-18 hours. The program automatically controls the opening of the cold air inlet door and the dehumidification window blades, and the circulating fan is kept at medium speed. The middle layer of tobacco leaves will turn white and half of the leaves will soften, while the top layer will turn yellow with green veins and the leaves will soften slightly.

[0009] Step 6: Increase the temperature at 1℃ / h to 44℃ for dry bulbs and maintain the temperature for 6-12 hours. During the temperature increase and stabilization period, manually open the cold air inlet to the maximum to continuously ventilate and dehumidify. When the wet bulb temperature is 31-33℃, adjust the circulating fan to high speed. Bake until half of the veins of the top layer of tobacco leaves turn white and the tips curl.

[0010] Step 7: Increase the temperature at 1℃ / h to a dry bulb temperature of 48℃ and stabilize it for 10-16 hours. During the temperature increase and stabilization period, manually keep the cold air inlet door at its maximum opening to continuously ventilate and dehumidify. Keep the wet bulb temperature at 31-33℃ and maintain the high speed of the circulating fan to promote leaf drying. Bake until half of the main vein of the top tobacco leaf turns white and half of the leaf is dry.

[0011] Step 8: Increase the temperature at 1℃ / h to 54℃ for dry bulb and stabilize for 12-18 hours. During the temperature increase and stabilization, manually keep the cold air inlet door open to the maximum and continue ventilation and dehumidification. Keep the wet bulb temperature at 31-33℃ and keep the circulating fan at high speed until the main vein of the top tobacco leaves is still green and the leaves are completely dry.

[0012] Step 9: Increase the temperature to 60℃ at 1℃ / h and maintain the temperature for 4-8 hours. Manually keep the cold air inlet door at the maximum opening and continue to ventilate and dehumidify. Keep the wet bulb temperature at 32-34℃ and keep the circulating fan at high speed until the main vein of the tobacco leaves is half dry.

[0013] Step 10: Increase the temperature to 65-68℃ at a rate of 1℃ / h and maintain the temperature for 24-36 hours. Manually keep the cold air inlet door at its maximum opening and continue ventilation and dehumidification. Keep the wet bulb temperature at 32-34℃ and maintain the high speed setting of the circulating fan until the main veins of the top layer of tobacco leaves are completely dry and then stop the fire.

[0014] However, traditional roasting techniques are prone to problems such as mold growth, mottled leaves, ash residue, black residue, floating green color, green veins, uneven color, and a large number of pale tobacco leaves after roasting. In particular, the problems of green and mixed tobacco leaves, uneven color, and pale color are more prominent, and it is necessary to improve them. Summary of the Invention

[0015] Based on the above, the present invention provides a biomass-based intensive curing and humidity control method, which is suitable for the tobacco curing process and can solve problems such as mold, mottled leaves, ash residue, black residue, floating green color, green veins, uneven color, and pale color that occur in traditional curing techniques, thereby improving the quality of tobacco curing.

[0016] The technical solution of this invention is: a biomass rising intensive baking and humidity control method, comprising the following steps:

[0017] The first step is to load the tobacco onto the kiln, close the doors and windows, set the baking process parameters, adjust the baking curve status indicator box to the initial position, adjust the circulating fan to low speed, and start baking.

[0018] The second step is to maintain the starting dry and wet bulb temperatures at 32℃ for 2 hours of preheating. After preheating the tobacco leaves, increase the temperature by 1℃ / h to 36℃ for the dry bulb and 35℃ for the wet bulb, and maintain the temperature for 6-12 hours. If the inner wall of the curing barn roof is damp, manually hang up two leaves on the upper part of each of the left and right exhaust windows to form symmetrical small exhaust vents to remove moisture from the roof. The program automatically controls the opening of the cold air inlet door and keeps the circulating fan at a low speed until the tips of the bottom leaves turn yellow and soft.

[0019] The third step is to raise the temperature at 1℃ / h to 38℃ for dry bulb and 35-37℃ for wet bulb, and bake at a stable temperature for 14-26 hours. Keep two leaves of each of the left and right dehumidification windows hanging up, and the program automatically controls the opening of the cold air inlet door. Keep the circulating fan at a low speed until the bottom tobacco leaves turn yellow and soften in a coordinated manner, reaching 80% yellow leaves and softened leaves.

[0020] The fourth step is to adjust the circulating fan to medium speed and raise the temperature to 40°C for dry bulb and 35-37°C for wet bulb at 1°C / 2h. Maintain the temperature for 10-16h and keep two leaves hanging on each side of the dehumidification window. The program will automatically control the opening of the cold air inlet door. Bake until the middle layer tobacco leaves are 80% yellow and the leaves are soft, and the bottom layer leaves are yellow with green veins and the main veins are soft.

[0021] Step 5: Increase the temperature by 1℃ / 2h to 42℃ for dry bulb and 35-37℃ for wet bulb, and maintain the temperature for 16-28h. If the temperature difference between the upper and lower wet bulbs exceeds 0.5℃ during the temperature stabilization period, hang up four leaves on the upper part of each of the left and right exhaust windows to form two small exhaust vents on each side, maintaining the humidity difference between the upper and lower shelves within 0.5℃. Manually control the opening of the cold air inlet door to continuously ventilate and dehumidify, maintaining the wet bulb temperature of the lower shelf at 35-37℃. Adjust the circulating fan to high speed to coordinate the yellowing and drying of the middle and lower layers, until the bottom layer of tobacco leaves reaches the point where the veins turn white and the tips curl, and the top layer reaches the point where the leaves are yellow with green veins and the main veins soften.

[0022] Step 6: Increase the temperature to 44°C dry bulb temperature by 1°C / 2-3 hours, and stabilize the temperature for 6-12 hours. During the temperature increase and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature value matches the target value and stabilizes. Continue ventilation and dehumidification to maintain the target wet bulb temperature at 35-37°C, and keep the circulating fan at high speed. If the wet bulb temperature difference between the upper and lower sheds exceeds 0.5°C, hang up six blades on each of the left and right dehumidification windows to form three small dehumidification outlets on each side, keeping the wet bulb humidity difference between the upper and lower sheds within 0.5°C. Bake until the veins of the top layer tobacco leaves turn white and the tips curl.

[0023] Step 7: Increase the temperature by 1℃ / 2-3h to a dry bulb temperature of 48℃ and stabilize it for 8-16h. During the temperature increase and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature value matches the target value and stabilizes. Continue ventilation to remove moisture and maintain the target wet bulb temperature of 35-37℃. Keep the circulating fan at high speed to promote leaf drying. If the wet bulb temperature difference between the upper and lower sheds is within 0.5℃, keep six leaves hanging on each of the left and right dehumidification windows and bake until the main vein of the top layer of tobacco leaves turns from green to white and half of the leaves are dry.

[0024] Step 8: Increase the temperature at 1℃ / 2h to a dry bulb temperature of 54℃ and stabilize it for 8-16 hours. During the temperature increase and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature matches the target value and stabilizes. Continue ventilation and dehumidification to maintain the target wet bulb temperature of 35-37℃ and keep the circulating fan running at high speed. If the wet bulb temperature difference between the upper and lower shelves exceeds 0.5℃, hang up all the leaves of the left and right dehumidification windows to keep the wet bulb temperature difference between the upper and lower shelves within 0.5℃. Continue baking until the main vein of the top layer of tobacco leaves turns yellow and the leaves are completely dry.

[0025] Step 9: Increase the temperature to 60℃ at 1℃ / h and stabilize it for 4-10 hours. Lower the four blades at the bottom of each of the left and right exhaust windows, manually close the cold air inlet door to reduce ventilation and dehumidification, maintain the wet bulb temperature at 36-38℃, adjust the circulating fan to medium speed, and bake until the main vein of the tobacco leaves shrinks and turns purple, and it is half dry.

[0026] Step 10: Increase the temperature to 65-68℃ at a rate of 1℃ / h and maintain the temperature for 20-36 hours. Lower all the blades of the left and right exhaust windows, manually close the cold air inlet door, leaving a gap, and reduce ventilation and dehumidification. Keep the wet bulb temperature at 37-39℃, adjust the circulating fan to low speed, and bake until the main veins of the top layer of tobacco leaves are completely dry before stopping the fire.

[0027] Preferably, in the first step, the tobacco leaves used in the same kiln are of the same variety, and the maturity of the tobacco leaves in the same layer is consistent. They are then loaded into high, medium, and low temperature layers according to their maturity levels, with the top layer being denser and the bottom layer sparser, ensuring that the layers are full and evenly packed.

[0028] Preferably, in the first step, the baking process parameters are ten target dry-bulb stable temperature points: the first stable temperature point has a dry-bulb temperature of 32℃ and a wet-bulb temperature of 32℃, stabilized for 2 hours, and a heating time of 4 hours; the second stable temperature point has a dry-bulb temperature of 36℃ and a wet-bulb temperature of 35℃, stabilized for 6-12 hours, and a heating time of 2 hours; the third stable temperature point has a dry-bulb temperature of 38℃ and a wet-bulb temperature of 35-37℃, stabilized for 12-24 hours, and a heating time of 4 hours; the fourth stable temperature point has a dry-bulb temperature of 40℃ and a wet-bulb temperature of 35-37℃, stabilized for 6-12 hours, and a heating time of 4 hours; and the fifth stable temperature point has a dry-bulb temperature of 42℃ and a wet-bulb temperature of 35-37℃, stabilized for 12-24 hours. The heating time is 4-6 hours. The sixth stable temperature point has a dry-bulb temperature of 44℃ and a wet-bulb temperature of 35-37℃. The temperature is stable for 6-12 hours, and the heating time is 8-12 hours. The seventh stable temperature point has a dry-bulb temperature of 48℃ and a wet-bulb temperature of 35-37℃. The temperature is stable for 8-16 hours, and the heating time is 12 hours. The eighth stable temperature point has a dry-bulb temperature of 54℃ and a wet-bulb temperature of 35-37℃. The temperature is stable for 8-16 hours, and the heating time is 6 hours. The ninth stable temperature point has a dry-bulb temperature of 60℃ and a wet-bulb temperature of 36-38℃. The temperature is stable for 4-10 hours, and the heating time is 5-8 hours. The tenth stable temperature point has a dry-bulb temperature of 65-68℃ and a wet-bulb temperature of 37-39℃. The temperature is stable for 20-36 hours.

[0029] Preferably, the circulating fan has a low speed setting of 720 r / min, a medium speed setting of 960 r / min, and a high speed setting of 1440 r / min.

[0030] The applicant's research revealed the following problems with the traditional biomass intensive curing technology: low-temperature moisturizing for slow yellowing, rapid heating, large ventilation, and low-humidity color fixing and drying. In the early yellowing stage, the dry-bulb temperature is 32-36℃, and the wet-bulb temperature is the same. The cold air inlet and exhaust windows are closed, resulting in poor ventilation and prolonged curing time. The bottom leaves remain 80% yellow without softening, while the top leaves are prone to mold and discoloration. In the middle yellowing stage, the dry-bulb temperature reaches 38℃, with a dry-wet difference of 1-1.5℃, requiring ventilation and dehumidification. In the initial stage of yellowing, the bottom layer of tobacco leaves is roasted until the veins are slightly soft and the leaflets are yellow. After roasting, they are prone to ash and black residue. In the later stage of yellowing, the dry-bulb temperature is 40-42℃, and the wet-bulb temperature is 38-40℃. Ventilation and dehumidification are minimal. The bottom layer of tobacco leaves is roasted until the veins turn white and the leaves are semi-soft. After roasting, they are prone to ash and black residue. The upper layer of tobacco leaves is also roasted until the veins are slightly soft and the leaflets are yellow. After roasting, they are prone to ash and black residue. In the early stage of color fixing, the dry-bulb temperature is increased to 44℃ at a rate of 1℃ per hour and stabilized for 6-12 hours. The cold air inlet is opened to the maximum, and the wet-bulb temperature is 31-33℃. The temperature is then increased by 1℃ per hour. The dry-bulb temperature is increased to 48℃ at a rate of ℃ and maintained for 10-16 hours, with the cold air inlet opening at maximum. The wet-bulb temperature is 31-33℃. The leaves are then baked until basically dry. This rapid heating and low humidity promotes drying and color setting of the tobacco leaves. After baking, many leaves exhibit uneven coloring, green veins, ash residue, black grime, or other defects. In the later stages of color setting, the dry-bulb temperature is increased to 54℃ at a rate of 1℃ per hour and maintained for 12-18 hours, with the cold air inlet opening at maximum and the wet-bulb temperature at 31-33℃. The leaves are then baked until completely dry. After roasting, there are more tobacco leaves with uneven color and large color difference; in the early stage of drying, the dry bulb temperature is increased to 60℃ at a rate of 1℃ per hour and maintained for 4-8 hours, the cold air inlet is kept at the maximum opening, the wet bulb temperature is 32-34℃, and roasting is carried out until the main vein is half dry, resulting in more light-colored tobacco leaves after roasting; in the later stage of drying, the dry bulb temperature is increased to 68℃ at a rate of 1℃ per hour and maintained for 24-36 hours, the cold air inlet is kept at the maximum opening, the wet bulb temperature is kept at 32-34℃, and roasting is carried out until the main vein is completely dry and the fire is stopped, resulting in more light-colored tobacco leaves after roasting.

[0031] The beneficial effects of this invention are as follows: Addressing the problems of mold, mottled leaves, ash residue, black residue, floating green color, green veins, uneven color, and excessive pale tobacco leaves after traditional curing techniques, this invention, based on the characteristics of tobacco curing, the density of tobacco packing, and changes during the curing process, reduces these problems in biomass-based intensive curing by manually adjusting the opening of the dehumidification window and the cold air inlet, along with adjustments to the circulating fan speed and wet-bulb temperature. According to the applicant's experiments, this invention can reduce these problems in biomass-based intensive curing, particularly solving the issues of green and impure tobacco leaves, uneven color, and pale color, thus improving the quality of tobacco curing. Detailed Implementation

[0032] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] First, let's describe the curing barn. The existing curing barn includes a heating chamber and a tobacco loading chamber. A cold air inlet is located on the upper part of the side of the heating chamber furthest from the tobacco loading chamber. The opening of the cold air inlet can be automatically controlled by the curing program or manually. On the upper part of both sides of the tobacco loading chamber closest to the heating chamber, dehumidification louvers are installed, with eight louvers on each side.

[0034] This invention discloses a biomass rising-type intensive baking and humidity control method, comprising the following steps:

[0035] The first step is pre-curing preparation. Before curing, check that the curing barn enclosure structure is airtight, the heating equipment is cleaned of accumulated ash and does not leak smoke, and the equipment is powered on and can work normally; pick tobacco leaves according to the current mature harvesting standards, classify and bundle (clamp), integrate and load them into the curing barn, and install the sensors in place.

[0036] In this step, the lower tobacco leaves are harvested when they are predominantly green with a hint of yellow, the middle tobacco leaves are harvested when they are yellowish-green or half yellowish-green, and the upper tobacco leaves are harvested when they are predominantly yellow with a hint of green. The leaves are then sorted and bundled, with each bundle containing approximately 60 bundles of leaves of the same type and maturity. Each bundle contains about 2-3 leaves, and each bundle contains the same number of leaves, ensuring they are fully and evenly packed. This ensures that the leaves on the same bundle exhibit consistent growth. The tobacco leaves are then integrated and loaded into the curing barn. The same variety of tobacco leaves are loaded into the same layer, ensuring consistent maturity. They are then placed in the high, medium, and low temperature layers of the curing barn according to their maturity level, with a denser top and sparser bottom, ensuring they are fully and evenly packed. Each layer contains approximately 100 bundles, ensuring consistent growth. Finally, the sensors are installed: a water bottle is filled with clean water, and clean, absorbent cotton yarn is used to wrap the wet-bulb thermometer bulb at the top and place the entire bottom of the yarn into the water bottle. The temperature and humidity sensors are installed in the corresponding positions on the bottom and top of the curing barn.

[0037] The second step is to set the parameters and ignite the oven for baking. After loading the oven, close the doors and windows. After powering on the electrical equipment, set the dry bulb temperature display box on the left side of the automatic controller to "lower oven". Set ten target dry bulb temperature stabilization points according to the current baking process. Combine the baking characteristics of the tobacco leaves in the lower, middle and upper parts and the tobacco loading density, and set the corresponding target wet bulb temperature, stabilization time, heating time and other parameters. The specific baking plan parameters are shown in Table 1 below. After setting the parameters, adjust the baking curve status indicator box to the initial position, adjust the circulating fan to low speed, and ignite the oven for baking.

[0038] Baking plan parameters

[0039]

[0040] In this step, the left side of the dry bulb temperature display box is set to "lower shed," displaying the actual temperature and humidity values ​​of the tobacco leaves in the lower shed during baking. The baking plan is designed to prevent large fluctuations in the baking temperature and humidity environment, which could affect the quality of the tobacco leaves. The baking curve status indicator box is adjusted to its initial position to prevent the indicator box from being in other positions, where the ignition temperature is high and the tobacco leaves become blanched. The circulating fan is adjusted to a low speed to open the ventilation duct and promote hot air circulation. The baking plan parameters include the last stable temperature point dry bulb temperature, the lower limit of baking time for lower tobacco leaves, the middle value for middle leaves, and the upper limit for upper leaves. The wet bulb temperature is the lower limit for tobacco leaves with poor baking characteristics in the upper and lower parts or dense packing, and the upper limit for tobacco leaves with good baking characteristics in the middle and upper parts or sparse packing.

[0041] The third step is to open the windows for drying, with automatic air intake. After preheating the tobacco leaves by maintaining an initial dry-bulb and wet-bulb temperature of 32℃ for 2 hours, maintain a temperature increase of 1℃ / hour, drying at 36℃ for the dry bulb and 35℃ for the wet bulb for 6-12 hours. If the inner wall of the drying room roof is damp, manually hang up two blades on the upper part of each of the left and right exhaust windows to form symmetrical small exhaust vents, removing moisture from the roof and preventing moisture from accumulating on the inner wall of the roof and dripping down, which can cause mold and mottled leaves. The program automatically controls the opening of the cold air intake door, and the circulating fan keeps at a low speed, drying until the tips of the bottom leaves turn yellow and soften.

[0042] Step 4: Stabilize temperature and humidity to soften the bottom layer of tobacco leaves. After the tips of the bottom layer of tobacco leaves turn yellow and soften, maintain a temperature increase of 1℃ / h, a dry bulb temperature of 38℃, and a wet bulb temperature of 35-37℃ for 14-26 hours. Keep two leaves on each side of the dehumidification window hanging, control the opening of the cold air inlet door according to the program, and keep the circulating fan at a low speed. During the temperature stabilization period, adjust the wet bulb temperature (if the bottom layer of tobacco leaves turns yellow slowly and loses water slowly, adjust the wet bulb temperature appropriately; if they turn yellow quickly and lose water slowly, adjust the wet bulb temperature appropriately) to coordinate the yellowing and softening of the bottom layer of tobacco leaves, achieving 80% yellowing and softening of the leaves. This prevents insufficient water loss and excessive dry matter consumption, which can lead to ash buildup and rotten leaves, or insufficient yellowing and excessive water loss, which can result in green curing.

[0043] Step 5: Adjust the airflow speed until the middle layer of tobacco leaves turns yellow and softens. Once the bottom layer of tobacco leaves is 80% yellow and softened, adjust the circulating fan to medium speed, appropriately increase the airflow speed between the leaves, and accelerate dehumidification to promote the yellowing and softening of the middle layer of tobacco leaves and the dehydration and yellowing of the bottom layer, preventing the tobacco leaves from becoming covered in ash, rotten leaves, or showing signs of aging. Maintain a temperature increase of 1℃ / 2 hours, a dry bulb temperature of 40℃, and a wet bulb temperature of 35-37℃ for 10-16 hours. Keep two leaves hanging on each side of the dehumidification window, and control the opening of the cold air inlet valve according to the program. The middle layer of tobacco leaves will turn 80% yellow and soften, and the bottom layer will turn yellow with softened veins.

[0044] Step 6: Adjust humidity levels and manually introduce airflow until the top layer of tobacco leaves turns yellow and softens. Once the middle layer of tobacco leaves is 80% yellow and softened, maintain a temperature increase of 1℃ / 2 hours, with dry bulbs at 42℃ and wet bulbs at 35-37℃ for 16-28 hours. During the temperature stabilization period, if the wet bulb temperature difference between the upper and lower shelves exceeds 0.5℃, hang four leaves from the upper part of each of the left and right exhaust windows to create two symmetrical small exhaust vents on each side, maintaining the humidity difference between the upper and lower shelves within 0.5℃ to prevent ash, lees, and curing of the upper layer of tobacco leaves. Manually control the opening of the cold air inlet (at this point, the cold air inlet opening is changed from program control to manual control to ensure uninterrupted airflow), continuously ventilating and dehumidifying to maintain the wet bulb temperature of the lower shelf at 35-37℃. Adjust the circulating fan to high speed to increase the airflow speed between the leaves, accelerate the dehumidification process, coordinate the yellowing and drying of the middle and lower layers, and prevent ash, lees, and curing of the upper layer of tobacco leaves. The bottom layer of tobacco leaves turns white at the branch veins and curls at the tips, while the top layer has yellow leaves with green veins and softened main veins.

[0045] Step 7: Stabilize humidity and raise temperature until the veins turn white, continue airflow and leaf curling. After the top layer of tobacco leaves turns yellow with green veins and the main vein softens, maintain a temperature of 1℃ for 2-3 hours to raise the temperature to a stable dry bulb temperature of 44℃. During the temperature raising and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature matches the target value and stabilizes. Continue ventilation to remove moisture, maintaining the target wet bulb temperature at 35-37℃. Keep the circulating fan at high speed to promote the drying of the middle and lower layers of leaves and the whitening of the main veins, preventing ash, black residue, green veins, and re-greening. If the wet bulb temperature difference between the upper and lower shelves exceeds 0.5℃, hang up six leaves on each of the left and right exhaust windows to form three small exhaust vents on each side, keeping the wet bulb humidity difference between the upper and lower shelves within 0.5℃ to prevent ash and black residue from forming on the upper tobacco leaves. Stabilize the temperature at 44℃ for 6-12 hours until the veins of the top layer of tobacco leaves turn white and the tips curl.

[0046] Step 8: Stabilize humidity and raise temperature until the main veins of the tobacco leaves turn white and the tips curl. Continue airflow to partially dry the leaves. After the veins of the top layer of tobacco leaves turn white and the tips curl, maintain a temperature of 1℃ for 2-3 hours to raise the temperature to a stable dry bulb temperature of 48℃. During the temperature rise and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature matches the target value and stabilizes. Continue ventilation to remove moisture, maintaining the target wet bulb temperature at 35-37℃. Keep the circulating fan at high speed to promote leaf drying and prevent dust, black spots, and green veins. If the wet bulb temperature difference between the upper and lower sheds is within 0.5℃, keep six leaves hanging on each of the left and right exhaust windows to promote the whitening of the main veins of the tobacco leaves, dry the leaves, and achieve a uniform and bright color. Maintain a stable temperature of 48℃ for 8-16 hours until the main veins of the tobacco leaves turn white and the leaves are half-dry.

[0047] Step 9: Stabilize humidity, increase humidity, and continuously ventilate until the leaves are completely dry. After the main veins of the top layer of tobacco leaves turn from green to white and the leaves are half-dry, maintain a temperature of 1℃ / 2 hours to increase the temperature to a stable dry-bulb temperature of 54℃. During the temperature increase and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet-bulb temperature matches the target value and stabilizes. Continuously ventilate to remove humidity, maintaining the target wet-bulb temperature of 35-37℃, and keep the circulating fan running at high speed. If the wet-bulb temperature difference between the upper and lower sheds exceeds 0.5℃, hang all the leaves of the left and right exhaust windows to reduce the humidity of the tobacco leaves in the lower shed, keeping the wet-bulb temperature difference between the upper and lower sheds within 0.5℃ to promote drying and color setting of the tobacco leaves and prevent scorching, green veins, and dark color. Baking at a stable temperature of 54℃ for 8-16 hours will result in the main veins of the tobacco leaves turning yellow and the leaves being completely dry.

[0048] Step 10: Reduce ventilation and dehumidification; the midrib shrinks and turns purple. After the midrib of the top layer of tobacco leaves turns yellow and the leaves are completely dry, maintain a temperature increase of 1℃ / h to a stable 60℃. Lower four leaves from the bottom of each of the left and right dehumidification windows, manually close the cold air inlet damper, reduce ventilation and dehumidification, maintain a wet-bulb temperature of 36-38℃, and adjust the circulating fan to medium speed to promote the drying of the tobacco veins and prevent the color from becoming pale. Baking at a stable 60℃ for 4-10 hours will cause the midrib of the tobacco leaves to shrink and turn purple, and the leaves to be half-dry. In this step, manually closing the dehumidification windows and cold air inlet damper, and adjusting the fan to medium speed, ensures that most of the moisture in the tobacco leaves has been removed. Appropriate humidification is beneficial for improving the color of the tobacco leaves and drying the midrib. It also prevents the sensor water tank from drying out, which would cause the cold air inlet damper to open wide, affecting the quality of tobacco curing and wasting fuel.

[0049] Step 11: Leave a gap in the vent and dry the main vein completely. After the main vein of the tobacco leaf shrinks and turns purple, and is half-dry, maintain a temperature increase of 1℃ / h to a stable temperature of 65-68℃. Lower all the blades of the left and right exhaust windows, manually close the cold air inlet vent, leaving a gap (manually close the cold air inlet vent, but do not close it completely, leave a small gap) to reduce ventilation and dehumidification. Maintain the wet bulb temperature at 37-39℃. Adjust the circulating fan to a low speed to promote the drying of the main vein, improve the color, save fuel, prevent the tobacco leaf color from being too pale due to low humidity, and prevent the tobacco leaf from turning red due to high humidity. Stop the fire too early to allow the leaves to recover. Maintain a stable temperature of 65-68℃ for 20-36 hours. Stop the fire when the main vein of the top layer of tobacco leaves is completely dry (the main vein from the stem end to the tip has completely shrunk and turned purple, and is dry enough to break easily when bent by hand).

[0050] The baking effect of the present invention will be verified by the following experiment:

[0051] The experiment was conducted in Liupanshui City, Guizhou Province in 2022. The tested flue-cured tobacco variety was Yunyan 87, and the upper leaves were used as the experimental material. The tested tobacco leaves were cultivated and managed according to the local standardized practices for high-quality tobacco production, and harvested at maturity according to the standards and procedures for tobacco leaf maturity. The tested curing barn was a rising, dense curing barn. A comparative experiment was conducted, using traditional curing technology as a control and the curing process of this invention as a comparative treatment. Except for the process conditions, all other factors, such as curing barn structure, tobacco variety, quantity, and packing density, were the same.

[0052] Traditional baking process:

[0053] The first step is to load the tobacco onto the kang (heated brick bed), set the baking plan parameters as shown in Table 2 below. After setting the parameters, adjust the baking curve status indicator box to the initial position, adjust the circulating fan to low speed, and start the baking process.

[0054] Table 2 Baking Plan Parameters

[0055]

[0056] The second step involves consistent temperature and humidity, followed by low-temperature yellowing and expansion. After the tips of the bottom tobacco leaves turn yellow, maintain an initial dry-bulb and wet-bulb temperature of 32℃ for 18 hours. Then, increase the temperature by 1℃ / h to 36℃ for both the dry-bulb and wet-bulb leaves. Maintain this temperature for 18 hours, with the program automatically controlling the opening of the cold air inlet and exhaust window blades. Keep the circulating fan at a low speed until the bottom tobacco leaves are 80% yellow and have expanded.

[0057] The third step is to lower the wet bulb temperature slightly, then automatically allow air to enter and exit the oven, until the bottom layer of yellow leaves is slightly soft. After the bottom layer is 80% yellow, maintain a temperature increase of 1℃ / h to 38℃ for dry bulb and 37℃ for wet bulb, and bake at a stable temperature for 18 hours. The program automatically controls the opening of the cold air inlet and exhaust window blades, and the circulating fan is kept at a low speed until the bottom layer of tobacco leaves has yellow veins and slightly soft leaves.

[0058] Step 4: Adjust the speed to promote yellowing, with automatic air intake and exhaust. The middle layer of yellow flakes will soften slightly. After the bottom layer of yellow flakes develops blue veins, adjust the circulating fan to medium speed and maintain a temperature increase of 1℃ / h to 40℃ for dry bulbs and 39℃ for wet bulbs. Maintain a stable temperature for 12 hours of baking. The program will automatically control the opening of the cold air intake door and the exhaust window blades. Bake until the middle layer of yellow flakes develops blue veins and the blades soften slightly, and the bottom layer reaches the point where the veins turn white and half of the blades soften.

[0059] Step 5: Automatic intake and exhaust, maintaining medium speed, until the top layer of yellow leaves is slightly softened. After the middle layer of yellow leaves develop green veins, maintain a temperature increase of 1℃ / h to 42℃ for dry bulb and 40℃ for wet bulb, and bake at a stable temperature for 18 hours. The program automatically controls the opening of the cold air inlet and exhaust window blades, and the circulating fan maintains medium speed until the middle layer of tobacco leaves reaches the point where the veins turn white and half of the leaves soften, and the top layer reaches the point where the yellow leaves develop green veins and the leaves are slightly softened.

[0060] Step 6: Rapidly increase temperature, maintain strong airflow, low humidity and high speed, until the top leaf veins are half-white and the leaves curl. After the top leaves turn yellow and the veins turn green, maintain a temperature increase of 1℃ / h until the dry bulb temperature reaches 44℃, and stabilize the temperature for 12 hours. During the temperature increase and stabilization period, manually open the cold air inlet to the maximum stable position, continuously ventilate and dehumidify, maintain the wet bulb temperature at 33℃, and adjust the circulating fan to high speed; bake until half of the top leaf veins turn white and the tips curl.

[0061] Step 7: Rapidly increase temperature, maintain strong airflow, low humidity and high speed, until the top leaf vein is half-white and the leaves are half-dry. After the top leaf tips are hooked and curled, maintain a temperature increase of 1℃ / h until the dry bulb temperature reaches 48℃ and stabilizes for 16 hours. During the temperature increase and stabilization period, manually maintain the maximum opening of the cold air inlet damper to continuously ventilate and remove moisture, maintain the wet bulb temperature at 33℃, and keep the circulating fan at high speed to promote leaf drying; bake until the top leaf vein turns half-white and the leaves are half-dry.

[0062] Step 8: Rapidly increase temperature, maintain strong airflow, low humidity and high speed until the top leaf veins are still green and the leaves are completely dry. After the top leaves are half dry, maintain a temperature increase of 1℃ / h until the dry bulb reaches 54℃ and remains stable for 18 hours. During the temperature increase and stabilization period, manually maintain the maximum opening of the cold air inlet damper to continuously ventilate and remove moisture, maintain the wet bulb temperature at 33℃, and keep the circulating fan at high speed until the top tobacco leaves have green veins and are completely dry.

[0063] Step 9: Maintain strong winds, low humidity, and high speed until the main veins are half-dry. After the top layer of tobacco leaves is completely dry, maintain a temperature of 1℃ / h to 60℃ and keep it stable for 8 hours. Manually maintain the maximum opening of the cold air inlet door to continuously ventilate and remove moisture, maintain the wet bulb temperature at 34℃, and keep the circulating fan at high speed until the main veins of the tobacco leaves are half-dry.

[0064] Step 10: Maintain strong winds, low humidity, and high speed until the main veins are completely dry. After the main veins of the tobacco leaves are half dry, maintain a temperature increase of 1℃ / h to 68℃ and stabilize the temperature for 36 hours. Manually maintain the maximum opening of the cold air inlet door to continuously ventilate and remove moisture, maintain the wet bulb temperature at 34℃, and keep the circulating fan at high speed until the main veins of the top layer of tobacco leaves are completely dry and then stop the fire.

[0065] Baking process of this invention:

[0066] The first step is to load the tobacco onto the kang (heated brick bed), set the baking plan parameters as shown in Table 3 below, and after the parameters are set, adjust the baking curve status indicator box to the initial position, adjust the circulating fan to the low speed setting, and start the baking process.

[0067] Table 3 Baking Plan Parameters

[0068]

[0069] The second step is to open the windows for curing with automatic air intake. After preheating the tobacco leaves by maintaining an initial dry-bulb and wet-bulb temperature of 32℃ for 2 hours, maintain a temperature increase of 1℃ / h, a dry-bulb temperature of 36℃, and a wet-bulb temperature of 35℃ for 6 hours. Open the dehumidification window blades to observe the moisture on the inner wall of the curing barn roof. Manually hang up two blades at the top of each of the left and right dehumidification windows to form symmetrical small dehumidification openings, removing moisture from the roof and preventing further accumulation of moisture on the inner wall of the curing barn roof, which can cause mold and mottled leaves. The program automatically controls the opening of the cold air inlet door, and the circulating fan maintains a low speed to promote the yellowing and softening of the leaf tips at the bottom. Maintain a stable temperature of 36℃ and a wet-bulb temperature of 35℃ for 12 hours, until the leaf tips of the bottom tobacco leaves turn yellow and soften.

[0070] The third step is to stabilize the temperature and humidity, resulting in a soft and yellowed bottom layer of tobacco leaves. After the tips of the bottom layer of tobacco leaves turn yellow and soften, maintain a temperature increase of 1℃ / h, a dry-bulb temperature of 38℃, and a wet-bulb temperature of 36℃ for 18 hours, until the bottom layer of tobacco leaves is 70% yellow and half-softened. Then adjust the wet-bulb temperature to 35℃ to promote a coordinated yellowing and softening of the bottom layer of tobacco leaves. Keep two leaves hanging on the upper part of each of the left and right dehumidification windows, and automatically control the opening of the cold air inlet door, keeping the circulating fan at a low speed. Maintain a dry-bulb temperature of 38℃ and a wet-bulb temperature of 35℃ for another 6 hours, until the bottom layer of tobacco leaves is 80% yellow and softened, preventing the tobacco leaves from becoming ashy due to insufficient water loss or from turning green due to insufficient yellowing.

[0071] Step 4: Adjust the wind speed to soften the middle layer of tobacco leaves. After the bottom layer of tobacco leaves has turned 80% yellow and softened, adjust the circulating fan to medium speed to promote the yellowing and softening of the middle layer of tobacco leaves and prevent ash buildup and brining. Maintain a temperature increase of 1℃ / 2 hours, dry bulb temperature of 40℃, and wet bulb temperature of 36℃ for 16 hours of baking. Keep two leaves hanging on each of the upper leaves of the left and right exhaust windows. The program automatically controls the opening of the cold air inlet. The middle layer of tobacco leaves will turn 80% yellow and soften, and the bottom layer will turn yellow and soften the main veins.

[0072] Step 5: Adjust humidity levels and manually introduce airflow until the top layer of tobacco leaves turns yellow and softens. After 80% of the middle layer tobacco leaves have turned yellow and softened, maintain a temperature increase of 1℃ / 2 hours, a dry bulb temperature of 42℃, and a wet bulb temperature of 36℃ for 6 hours of baking. Ensure the wet bulb temperature difference between the upper and lower shelves exceeds 0.5℃. Hang four leaves from the upper part of each of the left and right exhaust windows to create two symmetrical small exhaust vents on each side, maintaining the humidity difference between the upper and lower shelves within 0.5℃ to prevent ash buildup and burnt-green leaves. Manually control the opening of the cold air intake door for continuous ventilation and dehumidification, maintaining a wet bulb temperature of 36℃. Adjust the circulating fan to high speed to coordinate the yellowing and drying of the middle and lower layers, preventing ash buildup and burnt-green leaves. Maintain a dry bulb temperature of 42℃ and a wet bulb temperature of 36℃ for another 18 hours of baking. The bottom layer tobacco leaves will reach a point where the veins turn white and the tips curl, while the top layer will reach a point where the leaves are yellow with green veins and the main veins soften.

[0073] Step 6: Stabilize humidity and raise temperature until the veins turn white, continue airflow and leaf curling. After the top layer of tobacco leaves turns yellow with green veins and the main vein softens, maintain a temperature of 1℃ / 3h to raise the temperature to a stable dry bulb temperature of 44℃. During the temperature rise and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature matches the target value and stabilizes. Continue ventilation to remove moisture, maintaining the target wet bulb temperature at 36℃. Keep the circulating fan at high speed to promote the drying of the middle and lower layers of leaves and the whitening of the main veins, preventing ash buildup, evaporation, green veins, and re-greening. If the wet bulb temperature difference between the upper and lower shelves exceeds 0.5℃, hang up six leaves from each of the left and right exhaust windows to form three small exhaust vents on each side symmetrically, keeping the wet bulb humidity difference between the upper and lower shelves within 0.5℃ to prevent ash buildup and evaporation of the upper layer. Stabilize the temperature at 44℃ for 12h, until the veins of the top layer of tobacco leaves turn half white and the tips curl. Then maintain a wet bulb temperature of 36℃ and a dry bulb temperature of 44℃ for 6h, until the veins of the top layer of tobacco leaves are completely white and the tips curl.

[0074] Step 7: Stabilize humidity and raise temperature until the main veins of the tobacco leaves turn white, and continue airflow to partially dry the leaves. After the veins of the top layer of tobacco leaves turn white and the tips curl, maintain a temperature of 1℃ / 3h to raise the temperature to a stable dry bulb temperature of 48℃. During the temperature rise and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature matches the target value and stabilizes. Continue ventilation to remove moisture, maintaining a wet bulb temperature of 36℃. Keep the circulating fan at high speed to promote leaf drying, prevent dust accumulation, evaporation, and green veins. The wet bulb temperature difference between the upper and lower sheds should be within 0.5℃. Keep six leaves hanging on each of the left and right dehumidification windows to promote the whitening of the main veins of the tobacco leaves, semi-drying of the leaves, and uniform and bright color, preventing the tobacco leaves from darkening. Baking at a stable temperature of 48℃ for 18h will result in the main veins of the tobacco leaves turning white and the leaves being half-dry.

[0075] Step 8: Stabilize humidity, increase humidity, and continuously ventilate until the leaves are completely dry. After the main veins of the top layer of tobacco leaves turn from green to white and the leaves are half-dry, maintain a temperature of 1℃ / 2 hours to increase the temperature to a stable dry bulb temperature of 54℃. During the temperature increase and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature matches the target value and stabilizes. Continuously ventilate to remove humidity, maintaining a wet bulb temperature of 36℃, and keep the circulating fan running at high speed. If the wet bulb temperature difference between the upper and lower shelves exceeds 0.5℃, hang all the leaves of the left and right exhaust windows to keep the wet bulb temperature difference between the upper and lower shelves within 0.5℃, promoting the drying and color setting of the tobacco leaves and preventing steaming, green veins, and dark color. Bathe at a stable temperature of 54℃ for 20 hours until the main veins of the tobacco leaves turn yellow and the leaves are completely dry.

[0076] Step 9: Reduce ventilation and dehumidification; the midrib will shrink and turn purple. After the midrib of the top layer of tobacco leaves turns yellow and the leaves are completely dry, maintain a temperature increase of 1℃ / h to a stable 60℃. Lower four leaves from the bottom of each of the left and right dehumidification windows, manually close the cold air inlet damper to reduce ventilation and dehumidification, maintain a wet-bulb temperature of 37℃, and adjust the circulating fan to medium speed to promote the drying of the tobacco veins and prevent the tobacco leaves from becoming pale. Baking at a stable 60℃ for 10 hours will cause the midrib of the tobacco leaves to shrink and turn purple, and the leaves to be half-dry.

[0077] Step 10: Leave a gap in the air vents and allow the main veins to dry completely. After the main veins of the tobacco leaves shrink and turn purple, and are half-dried, maintain a temperature increase of 1℃ / h to a stable temperature of 68℃. Lower all the blades of the left and right exhaust windows, manually close the cold air inlet vents, leaving a gap to reduce ventilation and dehumidification. Maintain the wet-bulb temperature at 38℃, and adjust the circulating fan to a low speed to promote the drying of the main veins, improve color, save fuel, prevent the tobacco leaves from turning pale due to excessively low humidity, and prevent them from turning red due to excessively high humidity, thus preventing premature shutdown and tendon regeneration. Maintain a stable temperature of 68℃ for 36 hours, and shut off the fire when the main veins of the top layer of tobacco leaves are completely dry.

[0078] The following sections evaluate and analyze the tobacco leaves produced by the roasting method of this invention and the traditional roasting process from aspects such as tobacco leaf output value, appearance quality, and chemical composition.

[0079] Experimental results:

[0080] 1. Impact on tobacco production value

[0081] Compared with traditional baking technology, this invention increases the proportion of high-grade smoke by 1.55 percentage points, the proportion of medium-grade smoke by 1.21 percentage points, the average price by 0.45 yuan / kg, and the output value by 1048.5 yuan / hm². 2 .

[0082] Table 4 Comparison of Tobacco Leaf Output Value

[0083] project Percentage of premium-grade tobacco (%) Percentage of moderate smokers (%) Average price (RMB / kg) <![CDATA[Output value (yuan / hm 2 )]]> invention 66.26 29.88 27.29 61402.5 Tradition 64.71 28.67 26.84 60354

[0084] 2. Impact on the appearance quality of tobacco leaves

[0085] The appearance of the tobacco leaves after curing according to this invention is superior to that of traditional curing technology in terms of leaf structure, maturity, quality, oil content, and color. The color index is better (uneven color and pale color are included in the color index), the yellow tobacco rate is increased by 2.6 percentage points, the mixed color tobacco rate (moldy, mottled leaves, ash, and black residue are included in the mixed color rate) is reduced by 1.5 percentage points, and the green tobacco rate (floating green and green veins are included in the green tobacco rate) is reduced by 1.1 percentage points.

[0086] Table 5 Comparison of tobacco leaf appearance quality

[0087] project Blade structure Maturity identity Oil content Color Yellow smoke rate (%) Colored smoke rate (%) Green smoke rate (%) invention Still loose Mature Slightly thicker have medium and strong 96.7 2.1 1.2 Tradition Slightly dense Unripe, somewhat ripe, mature Thick, slightly thick Slightly, Yes middle 94.1 3.6 2.3

[0088] 3. Effects on the chemical composition of tobacco leaves

[0089] The tobacco leaves of this invention have higher total sugar and reducing sugar content and lower protein content after curing. Taking the upper leaves as an example, the total sugar content is 25.8% and the reducing sugar content is 13.2%, which are 11.1% and 5.7% higher than the traditional content, respectively. The protein content is 9.1%, which is 2.7% lower than the traditional content.

[0090] Table 6 Comparison of Chemical Components of Tobacco Leaves

[0091] project Total sugar (%) Reducing sugar (%) protein(%) invention 25.8 13.2 9.1 Tradition 14.7 7.5 11.8

[0092] 4. Evaluation of the tobacco curing effect

[0093] This invention can effectively improve the proportion of high-grade tobacco leaves, appearance quality, and chemical composition of tobacco leaves, thereby improving the industrial usability of tobacco leaves.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A biomass updraft dense drying conditioning method, characterized by, Includes the following steps: The first step is to load the tobacco onto the kiln, close the doors and windows, set the baking process parameters, adjust the baking curve status indicator box to the initial position, adjust the circulating fan to low speed, and start baking. The second step is to maintain the starting dry and wet bulb temperatures at 32℃ for 2 hours of preheating. After preheating the tobacco leaves, increase the temperature by 1℃ / h to 36℃ for the dry bulb and 35℃ for the wet bulb, and maintain the temperature for 6-12 hours. If the inner wall of the curing barn roof is damp, manually hang up two leaves on the upper part of each of the left and right exhaust windows to form symmetrical small exhaust vents to remove moisture from the roof. The program automatically controls the opening of the cold air inlet door and keeps the circulating fan at a low speed until the tips of the bottom leaves turn yellow and soft. The third step is to raise the temperature at 1℃ / h to 38℃ for dry bulb and 35-37℃ for wet bulb, and bake at a stable temperature for 14-26 hours. Keep two leaves of each of the left and right dehumidification windows hanging up, and the program automatically controls the opening of the cold air inlet door. Keep the circulating fan at a low speed until the bottom tobacco leaves turn yellow and soften in a coordinated manner, reaching 80% yellow leaves and softened leaves. The fourth step is to adjust the circulating fan to medium speed and raise the temperature to 40°C for dry bulb and 35-37°C for wet bulb at 1°C / 2h. Maintain the temperature for 10-16h and keep two leaves hanging on each side of the dehumidification window. The program will automatically control the opening of the cold air inlet door. Bake until the middle layer tobacco leaves are 80% yellow and the leaves are soft, and the bottom layer leaves are yellow with green veins and the main veins are soft. Step 5: Increase the temperature by 1℃ / 2h to 42℃ for dry bulb and 35-37℃ for wet bulb, and maintain the temperature for 16-28h. If the temperature difference between the upper and lower wet bulbs exceeds 0.5℃ during the temperature stabilization period, hang up four leaves on the upper part of each of the left and right exhaust windows to form two small exhaust vents on each side, maintaining the humidity difference between the upper and lower shelves within 0.5℃. Manually control the opening of the cold air inlet door to continuously ventilate and dehumidify, maintaining the wet bulb temperature of the lower shelf at 35-37℃. Adjust the circulating fan to high speed to coordinate the yellowing and drying of the middle and lower layers, until the bottom layer of tobacco leaves reaches the point where the veins turn white and the tips curl, and the top layer reaches the point where the leaves are yellow with green veins and the main veins soften. Step 6: Increase the temperature to 44°C dry bulb temperature by 1°C / 2-3 hours, and stabilize the temperature for 6-12 hours. During the temperature increase and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature value matches the target value and stabilizes. Continue ventilation and dehumidification to maintain the target wet bulb temperature at 35-37°C, and keep the circulating fan at high speed. If the wet bulb temperature difference between the upper and lower sheds exceeds 0.5°C, hang up six blades on each of the left and right dehumidification windows to form three small dehumidification outlets on each side, keeping the wet bulb humidity difference between the upper and lower sheds within 0.5°C. Bake until the veins of the top layer tobacco leaves turn white and the tips curl. Step 7: Increase the temperature by 1℃ / 2-3h to a dry bulb temperature of 48℃ and stabilize it for 8-16h. During the temperature increase and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature value matches the target value and stabilizes. Continue ventilation to remove moisture and maintain the target wet bulb temperature of 35-37℃. Keep the circulating fan at high speed to promote leaf drying. If the wet bulb temperature difference between the upper and lower sheds is within 0.5℃, keep six leaves hanging on each of the left and right dehumidification windows and bake until the main vein of the top layer of tobacco leaves turns from green to white and half of the leaves are dry. Step 8: Increase the temperature at 1℃ / 2h to a dry bulb temperature of 54℃ and stabilize it for 8-16 hours. During the temperature increase and stabilization period, manually and gradually increase the opening of the cold air inlet until the actual wet bulb temperature matches the target value and stabilizes. Continue ventilation and dehumidification to maintain the target wet bulb temperature of 35-37℃ and keep the circulating fan running at high speed. If the wet bulb temperature difference between the upper and lower shelves exceeds 0.5℃, hang up all the leaves of the left and right dehumidification windows to keep the wet bulb temperature difference between the upper and lower shelves within 0.5℃. Continue baking until the main vein of the top layer of tobacco leaves turns yellow and the leaves are completely dry. Step 9: Increase the temperature to 60℃ at 1℃ / h and stabilize it for 4-10 hours. Lower the four blades at the bottom of each of the left and right exhaust windows, manually close the cold air inlet door to reduce ventilation and dehumidification, maintain the wet bulb temperature at 36-38℃, adjust the circulating fan to medium speed, and bake until the main vein of the tobacco leaves shrinks and turns purple, and it is half dry. Step 10: Increase the temperature to 65-68℃ at a rate of 1℃ / h and maintain the temperature for 20-36 hours. Lower all the blades of the left and right exhaust windows, manually close the cold air inlet door, leaving a gap to reduce ventilation and dehumidification. Keep the wet bulb temperature at 37-39℃, adjust the circulating fan to low speed, and bake until the main veins of the top layer of tobacco leaves are completely dry before stopping the fire.

2. The biomass updraft fixed-bed densification torrefaction method according to claim 1, wherein, In the first step, the tobacco leaves used in the same kiln are of the same variety and have the same maturity level. They are then packed into high, medium, and low temperature layers according to their maturity level, with the top layer being denser and the bottom layer sparser, ensuring that the packing is full and even.

3. The biomass updraft fixed-bed densification torrefaction method according to claim 1, wherein, In the first step, the baking process parameters are ten target dry-bulb stable temperature points. The first stable temperature point has a dry-bulb temperature of 32℃ and a wet-bulb temperature of 32℃, with a stabilization time of 2 hours and a heating time of 4 hours. The second stable temperature point has a dry-bulb temperature of 36℃ and a wet-bulb temperature of 35℃, with a stabilization time of 6-12 hours and a heating time of 2 hours. The third stable temperature point has a dry-bulb temperature of 38℃ and a wet-bulb temperature of 35-37℃, with a stabilization time of 12-24 hours and a heating time of 4 hours. The fourth stable temperature point has a dry-bulb temperature of 40℃ and a wet-bulb temperature of 35-37℃, with a stabilization time of 6-12 hours and a heating time of 4 hours. The fifth stable temperature point has a dry-bulb temperature of 42℃ and a wet-bulb temperature of 35-37℃, with a stabilization time of 12-24 hours and a heating time of 4 hours. The temperature rises over a period of 4-6 hours. At the sixth stable temperature point, the dry-bulb temperature is 44℃ and the wet-bulb temperature is 35-37℃. The temperature remains stable for 6-12 hours, and the temperature rises over 8-12 hours. At the seventh stable temperature point, the dry-bulb temperature is 48℃ and the wet-bulb temperature is 35-37℃. The temperature remains stable for 8-16 hours, and the temperature rises over 12 hours. At the eighth stable temperature point, the dry-bulb temperature is 54℃ and the wet-bulb temperature is 35-37℃. The temperature remains stable for 8-16 hours, and the temperature rises over 6 hours. At the ninth stable temperature point, the dry-bulb temperature is 60℃ and the wet-bulb temperature is 36-38℃. The temperature remains stable for 4-10 hours, and the temperature rises over 5-8 hours. At the tenth stable temperature point, the dry-bulb temperature is 65-68℃ and the wet-bulb temperature is 37-39℃. The temperature remains stable for 20-36 hours.

4. The biomass updraft fixed-bed densification torrefaction method according to claim 1, wherein, The circulating fan has a low speed setting of 720 r / min, a medium speed setting of 960 r / min, and a high speed setting of 1440 r / min.

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